All 6 speakers are driven from the OEM radio.
Page 8W-47-4 of the service manual shows that the front outputs go to both the door speakers and the dash tweeters. They are in parallel and the tweeters use a simple capacitor to block the bass.
The rears and the door speakers get full range output.
The OEM sub (I have one) taps off the rear speaker signal and amplifies the bass. It does not effect the rear speaker signal.
The connector pinouts and wiring are shown in the power antenna guide on
www.ptdiy.net in the guides section.
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2002 Dream Cruiser #435 with: over 115hp nitrous, MX-5 "burp-free" shift mod, 2003 shifter, 2001 radio, 2001 Mopar subwoofer, MX-5 designed true cold-air intake, MX-5 designed double platinum spark plugs, shory antenna, much more....